If it turns out that the only way the rest of the regex can succeed is when the greedy construct in question matches nothing, well, that's perfectly fine, if zero matches are allowed (as with star, question, and {0,max} intervals). However, it turns out this way only if the requirements of some later subexpression force the issue. It's because the greedy quantifiers always (or, at least, try to) take more than they minimally need that they are called greedy.
Greediness has many useful (but sometimes troublesome) implications. It explains, for example, why [0-9]+ matches the full number in March·1998. Once the '1' has been matched, the plus has fulfilled its minimum requirement, but it's greedy, so it doesn't stop. So, it continues, and matches the '998' before being forced to stop by the end of the string. (Since [0-9] can't match the nothingness at the end of the string, the plus finally stops.)
p.s. All night without sleepness to taking care of cute DD........but the DD's heathy is awful........